1. Field of the Invention
The present invention relates to a wafer diameter/sectional shape measuring machine for measuring the diameter and the sectional shape of the wafer such as silicon serving as a raw material for a semiconductor element.
2. Description of the Related Art
A wafer such as silicon serving as a raw material for a semiconductor element, is produced in a way that the wafer is cut into a thin piece from an ingot by a slicing machine. Thereafter, the outer periphery thereof is chamfered by use of a wafer chamfering machine. An orientation flat or a notch is formed in the periphery of the wafer for positioning and orienting the wafer, and is chamfered also.
FIG. 8 shows an outer appearance of the wafer with the orientation flat. In FIG. 8, designated at D is the diameter of the circular part 11 of the wafer, and L an orientation flat diameter (a distance from the circular part 11 to the orientation flat 12 ). Moreover, FIG. 13 shows an outer appearance of the wafer with the notch. In FIG. 13, designated at D is the diameter of the circular part 11 of the wafer, .alpha. an opening angle of a notch 13, .delta. an inclination of the center of the notch 13 to the center of the circular part 11, and M is a notch distance (a distance from the circular part 11 to the notch 13). Incidentally, a circle at the notch is a circle for indicating this distance, therefore, it is not a part of the wafer.
FIG. 9 shows a sectional shape required for the outer periphery of the wafer. FIG. 9 shows that Bu and Bd are widths of chamfering; .theta. u and .theta. d are tapered angles; Ru and Rd have curved corners and t is an outer periphery (not pointed). T is a thickness of the wafer. The diameter D, the orientation flat diameter L, the notch distance M and the sectional shape have tolerances, and, when they fail to meet the tolerances, the wafer becomes defective.
Further, the outer periphery of the wafer as described above and as follows includes the circular part 11, and the orientation flat 12 or the notch 13 of the wafer.
In the wafer chamfering machine, the wafer is positioned at the center of the circular part 11, and the orientation flat 12 or the notch 13 on the position control station, thereafter, the wafer is sent to the processing station. In the processing station, the wafer is adsorbed and held by the wafer table by vacuum and the like, and the relative vertical position between the wafer table and the processing grindstone is set. Thereafter the wafer table and the processing grindstone are rotated relative to each other, whereby the outer periphery of the wafer is chamfered.
In this case, the processing conditions (the relative vertical position between the wafer table and the processing grindstone, the relative horizontal position between the wafer table and the processing grindstone, the rotational speed of the wafer table and the like) are adjusted previously, however, in order to properly process the diameter D, the orientation flat diameter L, the notch distance M and the sectional shape shown in FIGS. 8, 9 and 13 accurately, one wafer is test-processed, and then, the diameter D, the orientation flat diameter L and the notch distance M are measured with the dimensional measuring machine and the sectional shape is measured with the shape measuring machine and confirmed, respectively, and correction values are inputted to the processing machine in accordance with the measured data so as to readjust the processing conditions. Usually, this operation is repeated several times, and then, the mass production is started.
However, in the conventional method, in order to accurately adjust the processing conditions of the wafer chamfering, the wafer, which has been test-processed, is taken out from the wafer chamfering machine and measured by another measuring machine. Then, the correction values are inputted to the processing machine in accordance with the measured data and another un-processed wafer is attached to the wafer chamfering machine to test-process again. Usually, it is necessary to be repeat this operation, therefore, there is a problem in that it takes a long time to set the processing conditions of the wafer chamfering. Moreover, the diameter D, the orientation flat diameter L, the notch distance M and the sectional shape are measured with different measuring machines, therefore, there is another problem in that it takes a long time to measure them.
Further, when the processing is run continuously, it is likely that the diameter D, the orientation flat L, the notch distance M and the sectional shape of the wafer are not processed accurately because of the abrasions and the like from the processing grindstone, therefore, there are problems in that the processing conditions of the wafer chamfering must be adjusted by the same operation during mass production and all wafers must be inspected after the processing.